Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$94.39	8.153%	$102.0856	$102.09	$102.10	$102.10
Purchase #2	$245.83	5.551%	$259.476	$259.48	$259.50	$259.50
Purchase #3	$65.80	3.257%	$67.9431	$67.94	$67.95	$67.90
Purchase #4	$208.29	9.439%	$227.9505	$227.95	$227.95	$228.00
Purchase #5	$155.78	7.551%	$167.5429	$167.54	$167.55	$167.50
Purchase #6	$217.72	13.515%	$247.1449	$247.14	$247.15	$247.10
Purchase #7	$66.68	6.594%	$71.0769	$71.08	$71.10	$71.10
7 purchase totals =	$1,054.49		$1,143.2199	$1,143.22	$1,143.30	$1,143.20